Buggy code:
public class ResponseAssertion extends AbstractTestElement implements Serializable , Assertion { private static final Logger log = LoggingManager . getLoggerForClass ( ) ; private static final String TEST_FIELD = "Assertion.test_field" ; private static final String SAMPLE_URL = "Assertion.sample_label" ; private static final String RESPONSE_DATA = "Assertion.response_data" ; private static final String RESPONSE_CODE = "Assertion.response_code" ; private static final String RESPONSE_MESSAGE = "Assertion.response_message" ; private static final String ASSUME_SUCCESS = "Assertion.assume_success" ; private static final String TEST_STRINGS = "Asserion.test_strings" ; private static final String TEST_TYPE = "Assertion.test_type" ; private static final int MATCH = 1 << 0 ; static final int CONTAINS = 1 << 1 ; private static final int NOT = 1 << 2 ; private static final int EQUALS = 1 << 3 ; private static final int EQUALS_SECTION_DIFF_LEN = JMeterUtils . getPropDefault ( "assertion.equals_section_diff_len" , 100 ) ; private static final String EQUALS_DIFF_TRUNC = "..." ; private static final String RECEIVED_STR = "******<seq2seq4repair_space>received<seq2seq4repair_space>:<seq2seq4repair_space>" ; private static final String COMPARISON_STR = "******<seq2seq4repair_space>comparison:<seq2seq4repair_space>" ; private static final String DIFF_DELTA_START = JMeterUtils . getPropDefault ( "assertion.equals_diff_delta_start" , "[[[" ) ; private static final String DIFF_DELTA_END = JMeterUtils . getPropDefault ( "assertion.equals_diff_delta_end" , "]]]" ) ; public ResponseAssertion ( ) { } public void clear ( ) { } private void setTestField ( String testField ) { } public void setTestFieldURL ( ) { } public void setTestFieldResponseCode ( ) { } public void setTestFieldResponseData ( ) { } public void setTestFieldResponseMessage ( ) { } public boolean isTestFieldURL ( ) { } public boolean isTestFieldResponseCode ( ) { } public boolean isTestFieldResponseData ( ) { } public boolean isTestFieldResponseMessage ( ) { } private void setTestType ( int testType ) { } public void addTestString ( String testString ) { } public void clearTestStrings ( ) { } public AssertionResult getResult ( SampleResult response ) { } public String getTestField ( ) { } public int getTestType ( ) { } public CollectionProperty getTestStrings ( ) { } public boolean isEqualsType ( ) { } public boolean isContainsType ( ) { } public boolean isMatchType ( ) { } public boolean isNotType ( ) { } public void setToContainsType ( ) { } public void setToMatchType ( ) { } public void setToEqualsType ( ) { } public void setToNotType ( ) { } public void unsetNotType ( ) { } public boolean getAssumeSuccess ( ) { } public void setAssumeSuccess ( boolean b ) { } AssertionResult evaluateResponse ( SampleResult response ) { boolean pass = true ; boolean not = ( ( ResponseAssertion . NOT ) & ( getTestType ( ) ) ) > 0 ; <START_BUG> AssertionResult result = new AssertionResult ( ) ; <END_BUG> String toCheck = "" ; if ( getAssumeSuccess ( ) ) { response . setSuccessful ( true ) ; } if ( isTestFieldResponseData ( ) ) { String data = response . getResponseDataAsString ( ) ; toCheck = new StringBuffer ( response . getResponseHeaders ( ) ) . append ( data ) . toString ( ) ; } else if ( isTestFieldResponseCode ( ) ) { toCheck = response . getResponseCode ( ) ; } else if ( isTestFieldResponseMessage ( ) ) { toCheck = response . getResponseMessage ( ) ; } else { toCheck = response . getSamplerData ( ) ; if ( toCheck == null ) toCheck = "" ; } if ( ( toCheck . length ( ) ) == 0 ) { return result . setResultForNull ( ) ; } result . setFailure ( false ) ; result . setError ( false ) ; boolean contains = isContainsType ( ) ; boolean equals = isEqualsType ( ) ; boolean debugEnabled = ResponseAssertion . log . isDebugEnabled ( ) ; if ( debugEnabled ) { ResponseAssertion . log . debug ( ( ( "Type:" + ( contains ? "Contains" : "Match" ) ) + ( not ? "(not)" : "" ) ) ) ; } try { Perl5Matcher localMatcher = JMeterUtils . getMatcher ( ) ; PropertyIterator iter = getTestStrings ( ) . iterator ( ) ; while ( iter . hasNext ( ) ) { String stringPattern = iter . next ( ) . getStringValue ( ) ; Pattern pattern = JMeterUtils . getPatternCache ( ) . getPattern ( stringPattern , READ_ONLY_MASK ) ; boolean found ; if ( contains ) { found = localMatcher . contains ( toCheck , pattern ) ; } else if ( equals ) { found = toCheck . equals ( stringPattern ) ; } else { found = localMatcher . matches ( toCheck , pattern ) ; } pass = ( not ) ? ! found : found ; if ( ! pass ) { if ( debugEnabled ) { ResponseAssertion . log . debug ( ( "Failed:<seq2seq4repair_space>" + pattern ) ) ; } result . setFailure ( true ) ; result . setFailureMessage ( getFailText ( stringPattern , toCheck ) ) ; break ; } if ( debugEnabled ) { ResponseAssertion . log . debug ( ( "Passed:<seq2seq4repair_space>" + pattern ) ) ; } } } catch ( MalformedCachePatternException e ) { result . setError ( true ) ; result . setFailure ( false ) ; result . setFailureMessage ( ( "Bad<seq2seq4repair_space>test<seq2seq4repair_space>configuration<seq2seq4repair_space>" + e ) ) ; } return result ; } private String getFailText ( String stringPattern , String toCheck ) { } private static String trunc ( final boolean right , final String str ) { } private static StringBuffer equalsComparisonText ( final String received , final String comparison ) { } }

Fix:
AssertionResult result = new AssertionResult ( getName ( ) ) ;